The present invention relates to an inkjet recording apparatus, which ejects ink from nozzles and attaches the ink to a recording medium, thereby recording information.
Inkjet recording apparatus are capable of printing high-quality letters at a high speed and at a low cost. The apparatus are employed in copy machines, facsimile machines, printers and word-processors, and are thus widely used as information recording apparatus in offices as well as for personal use. Various techniques have been proposed to improve the inkjet recording apparatus, and nowadays these techniques still focus on higher speed recording, higher resolution, and full-color printing.
The following recording methods are available in inkjet recording: a method employing an electro-thermal transducing element, such as a heating resistor, as an energy-generating-means for expelling color material; a method employing an electro-mechanical transducing element such as a piezo element; an electrostatic method employing electrical energy as it is; and the like. Regarding a recording head employed in the apparatus, a serial scanning head has been commercialized. This head is mounted to a carriage and movable in a direction (main scanning direction) orthogonal to a transfer direction of recording paper (sub-scanning direction).
As a means for high speed recording, a dc motor is employed in the apparatus as a transfer motor for driving a transfer roller which transfers recording paper. This dc motor provides for easy speed adjustment and relatively large torque. A rotary detector is provided for detecting a rotating angle of the transfer motor in order to correctly control the feeding amount of the recording paper. On the rotary detector, radially extending slits are formed along the entire rim of the rotary detector at equal intervals.
The rotary detector is disposed coaxially with any gear (rotating member) of a transmission gear-train (driving force transmitting machine) which is placed between the transfer motor and the transfer roller. The transmission gear-train transmits the driving force of the transfer motor to the transfer roller.
The structure of the conventional inkjet recording apparatus discussed above has the following problems. The first problem relates to damage of the rotary detector. The rotary detector is often formed of thin plastic members. Such a delicate detector is vulnerable to being damaged due to a careless mistake by an operator at an apparatus assembly line, e.g., a shock by collision with another member. If the rotary detector is damaged, it is impossible to detect a rotating angle with a detecting sensor, or if the rotary detector is deformed, the rotating face of the detector shakes, and it is impossible to detect a correct rotating angle.
The second problem refers to stains on the rotary detector. The rotary detector can detect a rotating angle at greater accuracy with a larger diameter. However, the larger diameter for the greater accuracy prevents the apparatus from being downsized. When a high-quality letter is printed at a high speed, the recording head moves rapidly and the nozzle ejects smaller amount of ink, and thus the ink tends to scatter. Then the scattered ink attaches to the rotary detector, thereby producing an error in detecting a rotating angle. A smaller diameter of the rotary detector would avoid this problem; however, the smaller detector would produce another problem, i.e., lowering the accuracy of detecting a rotating angle.
The third problem relates to eccentricity of the rotary detector. The rotary detector must be mounted to a rotating shaft without eccentricity both in radial and thrust directions. Therefore, it is preferable to be to able check the eccentricity of the detector with ease.
The fourth problem relates to the size of the rotary detector. For detecting a rotating angle of the transfer motor, it is required to optically detect, with a detecting sensor, a number of slits of the rotary detector as the rotary detector is rotated by the transfer motor. When the detecting sensor is a transmission type sensor, its light-emitting-section and light-receiving-section are placed at both sides of the rotary detector, and the detecting sensor is mounted to the rim of the rotary detector. As a result, the detecting sensor protrudes largely in the radial direction compared with the gear disposed coaxially with the rotary detector. This structure is not preferable because it goes against the goal of downsizing the apparatus.
An objective of the present invention is to overcome the first problem discussed above, and to provide an inkjet recording apparatus which can avoid damage or deformation during assembly of the rotary detector to be mounted to a driving-force-transmitting-machine. The inkjet recording apparatus of the present invention comprises the following elements:
(a) a carriage disposed to be movable reciprocally in parallel with a main scanning direction;
(b) a recording head mounted to the carriage, for ejecting ink from a plurality of nozzles;
(c) a transferring machine for transferring a recording medium, to which the ink ejected from the recording head attaches thereby forming an image, in a sub-scanning direction orthogonal to the main scanning direction;
(d) a driving machine for operating the transferring machine;
(e) a driving force transmitting machine disposed between the driving machine and the transferring machine, for transmitting driving force of the driving machine to the transferring machine;
(f) a rotary detector disposed within a height of the driving force transmitting machine, and mounted coaxially with the rotary shaft of any one of rotary members constituting the driving force transmitting machine; and
(g) a detecting sensor for detecting a rotating angle of the rotary detector.
This structure allows the rotary detector to avoid colliding with other members during assembly of the apparatus even if the other members collide with elements of the driving force transmitting machine. Thus the rotary detector is prevented from being damaged or deformed by a collision.
The present invention overcomes the second and third problems discussed previously, and aims to provide an inkjet recording apparatus which can detect the rotating angle of the rotary detector with high accuracy, and yet, downsize the rotary detector. Besides, the apparatus can check eccentricity of the rotary detector mounted to the rotating shaft with ease.
The inkjet recording apparatus of the present invention comprises the following elements:
(a) a carriage disposed to be movable reciprocally in parallel with a main scanning direction;
(b) a recording head mounted to the carriage, for ejecting ink from a plurality of nozzles;
(c) a transferring machine for transferring a recording medium, to which the ink ejected from the recording head attaches thereby forming an image, in a sub-scanning direction orthogonal to the main scanning direction;
(d) a driving machine for operating the transferring machine;
(e) a driving force transmitting machine disposed between the driving machine and the transferring machine, for transmitting driving force of the driving machine to the transferring machine;
(f) a rotary detector mounted coaxially with a rotary shaft of any one of gears constituting the driving force transmitting machine, and slitsxe2x80x94extending in the radial direction of the detectorxe2x80x94being provided on the entire rim of the detector at equal intervals, and at least a part of the slits being disposed within a height of a tooth form of the gears; and
(g) a detecting sensor for detecting a rotating angle of the rotary detector by detecting a number of slits of the rotary member during rotation of the rotary detector.
Since at least a part of the slits of the rotary detector are placed within the height of tooth form of the gears, this structure allows the rotary detector to be accurately detected and downsized. Further, rotating conditions of the rotary detector can be compared with that of the gears by rotating the shaft, so that the eccentricity of the rotary detector can be checked with ease.
The present invention overcomes the fourth problem discussed previously, and aims to provide an inkjet recording apparatus having a transmission type detecting sensor disposed with respect to the rotary detector mounted coaxially with a rotary member. In this transmission type detecting sensor, a radially outward protrusion amount of the sensor with respect to the rotary member can be limited. The inkjet recording apparatus of the present invention comprises the following elements:
(a) a carriage disposed to be movable reciprocally in parallel with a main scanning direction;
(b) a recording head mounted to the carriage, for ejecting ink from a plurality of nozzles;
(c) a transferring machine for transferring a recording medium, to which the ink ejected from the recording head attaches thereby forming an image, in a sub-scanning direction orthogonal to the main scanning direction;
(d) a driving machine for operating the transferring machine;
(e) a driving force transmitting machine disposed between the driving machine and the transferring machine, for transmitting driving force of the driving machine to the transferring machine;
(f) a rotary detector mounted coaxially with a rotary shaft of any one of the rotary members constituting the driving force transmitting machine, and slitsxe2x80x94extending in the radial direction of the detectorxe2x80x94being provided on the entire rim of the detector at equal intervals; and
(g) a detecting sensor including:
(g-1) a light-emitting-section for irradiating a beam of detecting light to the slits on the rotating detector; and
(g-2) a light-receiving-section for receiving the beam of detecting light irradiated from the light-emitting-section, and disposed opposite to the light-emitting-section with respect to the rotary detector.
This sensor recognizes light-shading and light-transmission of the detecting light at the light-receiving-section, thereby detecting the rotating angle of the rotary detector. The light-shading and light-transmission of the detecting light is produced when the rotary detector rotates and the slits move. Either one of the light-emitting-section or the light-receiving-section is disposed between the rotating member and the rotary detector. This structure allows the rotary detector to have approximately the same diameter as the rotary member. Thus the detecting sensor disposed with respect to the rotary detector can limit the radially outward protrusion amount of the rotary member.